Many systems include imaging devices to sense and capture optical images that can be electronically converted to a digital representation of the image. These image sensors include an array of photo-sensitive devices such as photodiodes, photo-transistors, photoconductors, or photogates, fabricated on, for example, a complementary metal oxide semiconductor (CMOS) device. The photo-sensitive devices are arranged as an array of pixel cells in a focal plane. Each photo-sensitive device is sensitive to light in such a way that it can create an electrical charge that is proportional to the intensity of light striking the photo-sensitive device. The overall image captured by an image sensor includes many pixels arranged in an array such that each pixel detects the light intensity at the location of that pixel.
Active pixel arrays are conventionally configured with the sensor element and additional circuitry. In many CMOS image sensors, this additional circuitry is generally configured to convert the charge accumulated on the photo-sensitive device to a voltage and possibly amplify or buffer that voltage for sensing.
In conventional implementations, the additional circuitry is dedicated to these tasks of conversion to a voltage, buffering, and amplifying.